This invention generally relates to control methods useful with heavy duty vehicle transmissions that allow a driver to manually select an automatically implemented shift.
Heavy duty vehicles such as trucks typically include a multi-speed transmission that is manually controlled by the driver. The driver utilizes a manual stick shift and clutch to select one of several transmission gears depending upon the driving conditions, for example. The manual stick shift allows the driver to select from the various transmission gears, which vary the ratio between the input speeds of the transmission from the engine and the output speed of the transmission. Conventional shifting operations are typically difficult and cumbersome. They often require a high level of skill from the driver. As trucks have become more complex, the difficulties in shifting the transmission have also increased.
More recently, systems have been proposed to simplify the task of shifting the transmission. Such systems allow a driver to move a shift lever in one of two directions or to push buttons to indicate a desired shift. An electronic controller determines the desired gear ratio and operates an automatic shifting module to change the transmission into the desired gear ratio. Such systems have advantages in that they can simplify the task of driving a heavy duty vehicle.
The nature of a transmission associated with a heavy duty vehicle requires a variety of controlling strategies that must be implemented by the electronic controller to effect appropriate transmission operation. One situation where this is true is providing appropriate feedback to the driver of the vehicle regarding the status or condition of the transmission. This invention includes a method of providing the driver an indication of when the driver needs to take action such as manual clutch operation to ensure that the transmission is engaged into a desired gear. This invention also addresses the situations where a new gear must be engaged after the vehicle has been stopped or was coasting.